1. Field of the Invention
The present invention relates to a waist support of a dual-layer chair back, more particularly one, which allows a person to move it up and down easily to adjust its position while he is seated in the chair.
2. Brief Description of the Prior Art
Chair backs are usually made by means of wrapping leather or cloth around wooden or plastic board-shaped materials. Such chair backs are likely to make the sitters feel hot and uncomfortable at their backs, especially in summer, because air cannot travel through them. Another chair back is provided, which is comprised of a frame, and a mesh having large elasticity and secured over a space within the frame. Such mesh chair back allows air to travel through it therefore the sitter won't feel uncomfortably hot at his back even if he has been sitting on the chair for a long period of time in summer. However, the sitter is prone to have sore waist and painful back after having been seated in the chair for a long period of time because the chair back will contact the sitter's back only at the mesh part thereof, which can't support the sitter's back in a proper position effectively.
U.S. Pat. No. 6,588,842 disclosed a backrest of a chair in FIGS. 19 and 20, which includes a backrest frame, and a brace member connected to the backrest frame for providing support to the lumbar region of a sitter's back. The brace member is attached to the backrest frame by a pair of swivel connectors, which are mounted to the ends of the brace member, which have substantially identical structure; one of the connectors has several vertically aligned hook members extending perpendicularly outward from a plate for grasping the frame edge; a pivot rod extends perpendicularly inward from the plate and is received by an insert in a ball and socket type arrangement; the insert is mounted within a cavity in the brace member and has several annular ribs, which are received by corresponding annular grooves in the cavity to prevent axial displacement of the insert; the pivot rod is preferably mounted within the insert with sufficient frictional engagement to require manipulation of the brace member in order to pivot the brace member. Thus, the brace member can be adjusted to such an orientation in relation to the backrest frame as to suit the sitter.
The above chair backrest has the following disadvantages: First, the sitter isn't allowed to change the position of the brace member when seated on the chair; the sitter has to be away from the seat in order to be able to change the position of the brace member, and he has to sit back in the chair to find out whether the new position of the brace member suits him after adjustment; consequently, the sitter might have to stand up and sit down several times before he manages to move the brace member to a suitable position. Second, it takes relatively much labor, time and cost to manufacture and assemble the brace member because the brace member consists of many parts, and has a relatively complicated structure.